1. ECE 566- Parallel and Distributed Technology
Distributed Objects: CORBA/Java
RMI
Manish Parashar
parashar@ece.rutgers.edu
Department of Electrical &
Computer Engineering
Rutgers University

2. Distributed Objects: Goals
• Let any object reside anywhere in the
network, and allow an application to
interact with these objects exactly in the
same way as they do with a local objects
• Provide the ability to construct an object on
one host and transmit it to another host
• Enable an agent on one host to create a new
object on another host.
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3. Distributed Objects: Operations
• Locate remote object
• Creating remote objects
• Invoke methods on remote objects
• Obtain results from a remote method
invocation
• Delete remote object
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4. Distributed Objects: Properties
• Object locator
• Communication
– data type
– data representation
– synchronous/asynchronous
• State Persistence
• Security
• Reliability/Availability
• Load Balancing
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5. Java RMI
• Components
– Object Interfaces
• extends the Remote interface
– Server side implementation of the interface
• extends the java.rmi.server.UnicastRemoteObject
– RMI registry
– rmic compiler for stub and skeleton generation
• Others Issues
– Serialization
– Exception handling
– Constructors
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6. Java RMI: Object Interfaces
import java.rmi.Remote;
import java.rmi.RemoteException;
public interface DataRetrieval extends Remote
{
String GetData()
throws RemoteException;
}
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7. Java RMI: Server Implementation
import DataRetrieval;
import java.rmi.Naming;
import java.rmi.RemoteException;
import java.rmi.RMISecurityManager;
import java.rmi.server.UnicastRemoteObject; public String GetData()
import java.net.InetAddress; throws RemoteException
{
String client = null;
public class DataRetrievalImpl
extends UnicastRemoteObject try
implements DataRetrieval {
client = getClientHost();
{ }
private int call; catch(Exception e)
{
System.out.println(quot;exception: quot; + e);
public DataRetrievalImpl() client = quot;unknownquot;;
throws RemoteException }
{ call++;
super(); System.out.println(client + quot;
call = 0; request, data is:quot; + call);
} return quot;data is:quot; + call;
}
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8. Java RMI: Server Implementation
public static void main(String args[])
{
System.out.println(quot;Started server...quot;);
try
{
InetAddress host = InetAddress.getLocalHost();
String name = quot;//quot; + host.getHostName() + quot;/DataRetrievalquot;;
System.out.println(quot;binding to quot; + name);
System.setSecurityManager(new RMISecurityManager());
DataRetrievalImpl data = new DataRetrievalImpl();
Naming.rebind(name,data);
}
catch(Exception e)
{
System.out.println(quot;exception: quot; + e);
}
}
}
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9. Java RMI: Client
import DataRetrieval;
import java.rmi.Naming;
public class DataRetrievalClient
{
public static void main(String[] args)
{
if (args.length != 1)
{
System.out.println(quot;Please give server namequot;);
return;
}
try
{
DataRetrieval data = null;
String name = quot;rmi://quot; + args[0] + quot;/DataRetrievalquot;;
data = (DataRetrieval)Naming.lookup(name);
String reply;
reply = data.GetData();
System.out.println(quot;Got quot;+reply);
}
catch(Exception e)
{
System.out.println(quot;Exception quot;+e);
}
System.exit(0);
}
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}
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10. Java RMI: Registry/rmic
• RMI registry serves the role of the object manager
• % rmiregistry
• % rmiregistry <port #> // default is 1099
• Addressing a remote object
MyObject obj1 =
(MyObject)Naming.lookup(“rmi://objecthost.myorg.com/Object1);
MyObject obj1 =
(MyObject)Naming.lookup(“rmi://objecthost.myorg.com:2099/Object1);
• rmic compiler
• rmic serversideimpl
• generates client stub and server skeleton
• bootstraps off java bytecode
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11. CORBA
• Object Request Broker (ORB)
– enable clients and server objects to interact
– provide servers
• naming services, security services, …
• Interface Definition Language (IDL)
• Dynamic Invocation Interface (DII)
– Interface repository
• Internet Inter-Orb Protocol (IIOP)
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12. CORBA Solver
• Generate IDL description
• Generate client stub
• idltojava -f client Solver.idl
• generates Base Interface, holder classes & client stubs
package DCJ.examples;
public class _SolverStub
extends org.omg.CORBA.portable.ObjectImpl
implements DCJ.examples.Solver {
package DCJ.examples;
public class _ProblemSetStub
extends org.omg.CORBA.portable.ObjectImpl
implements DCJ.examples.ProblemSet {
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13. CORBA Solver
• Generate server skeleton and implementation
• idltojava -f server Solver.idl
• generates abstract base class for remote implementation
package DCJ.examples;
public abstract class _ProblemSetImplBase extends org.omg.CORBA.portable.ObjectImpl
implements DCJ.examples.ProblemSet,
org.omg.CORBA.portable.Skeleton {
package DCJ.examples;
public abstract class _SolverImplBase extends org.omg.CORBA.portable.ObjectImpl
implements DCJ.examples.Solver,
org.omg.CORBA.portable.Skeleton {
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14. CORBA Solver
• Implement remote object
• Implement client
• Start name server
• nameserve -ORBInitialport 1050
• Run Server
• Run Client
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